leveldb: change wether to whether (#139)
diff --git a/leveldb/db_compaction.go b/leveldb/db_compaction.go
index 9664e64..5553202 100644
--- a/leveldb/db_compaction.go
+++ b/leveldb/db_compaction.go
@@ -172,7 +172,7 @@
 		disableBackoff = db.s.o.GetDisableCompactionBackoff()
 	)
 	for n := 0; ; n++ {
-		// Check wether the DB is closed.
+		// Check whether the DB is closed.
 		if db.isClosed() {
 			db.logf("%s exiting", name)
 			db.compactionExitTransact()